The BBC has disclosed that Dr David Kelly was the principal source for its controversial report claiming Downing Street "sexed up" an Iraq weapons dossier.
David Kelly facing MPs last week
BBC director of news Richard Sambrook broke the news after speaking to the family of the Iraq weapons expert, who was found dead on Friday.
He said the corporation believed it correctly interpreted and reported the information obtained from Dr Kelly during interviews.
BBC journalist Andrew Gilligan, the author of the report, added that Dr Kelly had not been "misquoted or misrepresented".
Mr Sambrook said the BBC had, until now, owed Dr Kelly a duty of confidentiality and was "profoundly sorry" that his involvement as the source for the reports had ended in tragedy.
Prime Minister Tony Blair, speaking as he left Korea for China, said: "I am pleased that the BBC has made this announcement. Whatever the differences, no one wanted this tragedy to happen.
"I know that everyone, including the BBC, have been shocked by it. The independent Hutton Inquiry has been set up, it will establish the facts.
"In the meantime our attitude should be one of respect and restraint, no recrimination, with the Kelly family uppermost in our minds at this time."
Earlier Mr Blair said he would accept responsibility for all the actions of government ministers and officials, but ruled out recalling Parliament.
Police confirmed on Saturday Dr Kelly, a senior Ministry of Defence adviser, had bled to death from a cut to his wrist.
In an e-mail reportedly sent to a New York Times journalist hours before his death, Dr Kelly had apparently warned of "many dark actors playing games".
The Sunday Times says Dr Kelly told one of its reporters that he felt betrayed by the leaking of his name by the Ministry of Defence and was under "intolerable" pressure by being placed at the centre of the weapons row.
Last week Dr Kelly had told MPs he had spoken to Mr Gilligan, but said he did not believe he was the main source for a story about claims that a dossier on Iraq had been "sexed up" to boost public support for military action.
He told the MPs: "From the conversation I had I don't see how he could make the authoritative statement he was making from the comments I made."
According to television journalist Tom Mangold, a friend, Dr Kelly believed he was the source for about 60% of Mr Gilligan's report.
The government has set up an independent judicial inquiry, led by Lord Hutton, into the circumstances surrounding Dr Kelly's death. Both Mr Blair and the BBC have said they will cooperate fully.
The BBC statement prompted Dr Kelly's local MP, Tory Robert Jackson, to call for the resignation of the BBC chairman Gavyn Davies.
Ex-Labour minister Glenda Jackson has called for Tony Blair to quit, saying the blame for Dr Kelly's death lay with Downing Street, which, she said, used a battle with the BBC to divert attention from the failure to find weapons of mass destruction in Iraq.
Tory leader Iain Duncan Smith has called for Parliament to be recalled and for a broadening of the inquiry to investigate the government's handling of intelligence on Iraq.
But the prime minister told Sky News' Sunday With Adam Boulton programme that a recall of Parliament would "generate more heat than light" and that Dr Kelly's family should be allowed time to grieve.
Mr Blair said he would take responsibility for the actions of officials such as his communications director Alastair Campbell: "In the end the government is my responsibility and I can assure you the judge will be able to get to what facts, what people, what papers he wants."
He added: "At the present time this is far more something to do with the personal tragedy of Dr Kelly and I think that's actually what should be uppermost in our minds and has been in mine."
Asked if he had the appetite to go on as prime minister, Mr Blair replied: "Absolutely."
Dr Kelly's family said he was a "loving, private and dignified" man and appealed for time to grieve.
His body was discovered in woodland near his Oxfordshire home on Friday morning, with a knife and a packet of painkillers close by.
Richard Butler, former chief UN weapons inspector, said it appeared the British, American and Australian governments had "pumped up" the threat in the run-up to war.
Mr Butler told BBC Radio 4's The World This Weekend that Dr Kelly, a friend and colleague, was a "good man... of probity and integrity".
"It follows logically from that, if he thought that things were being pumped up, he would have objected to it."
Dr Kelly is survived by his wife, Janice, and three daughters Sian, 32, and 30-year-old twins Rachel and Ellen.